In my earlier U.S. Pat. No. 4,699,432 I describe a wheel usable on a standard quad, that is four-wheel, roller skate whose running surface is formed by two different materials. A hard resin forms a cylindrical base that is provided with a plurality of set-in plugs of a substantially softer resin, or a strip of harder material is provided that runs along the center of the ground-engaging surface. The softer resin provides improved traction.
Such an arrangement does provide improved performance on a quad roller skate as regards side-to-side traction but does exact some loss in performance as regards straight-ahead travel in that the soft material slows the wheel down. If such a wheel is used on an in-line roller skate or on a bicycle wheel, when the wheel is turned during stopping or turning to engage the ground with its side wall, the added traction of this system is completely lost. Under these circumstances only the hard material of the wheel engages the ground so there is no added traction.